Steroid hormone concentrations and physiological toxicity of water from selected dams in Namibia

Abstract

Namibia is a semi-arid to arid country and has most of its surface water in dams built on ephemeral rivers. Whilst water quality is often measured in terms of bacterial contamination and general physico-chemical characteristics, this study extends water quality assessment to include steroid hormone presence and potential physiological toxicity. This is the first study to determine these parameters in dams in Namibia at various stages of the seasons. Seven bioassays were used to determine oestradiol (E₂), oestrone (E₁) and testosterone (T) concentrations, as well as neurotoxicity, cytotoxicity and immunotoxicity, in water sampled during 2010 and 2011. Oestradiol and E₁ concentrations of up to 7.2 pg ml^–1 and 7.6 pg ml^–1, respectively, were recorded. Testosterone concentrations measured up to 19 pg ml^–1. No cytotoxic effects were detected, while acetylcholinesterase (AChE) inhibition assays indicated low neurotoxic effects in Goreangab Dam (18% AChE inhibition) and no neurotoxic effects in other samples. The immune system biomarker interleukin-6 was high in all samples (457 pg ml^–1 ; SD 54), with interleukin-10 being high only at Avis (46 pg ml^–1), Goreangab (74 pg ml^–1) and Swakoppoort (81 pg ml^–1) dams. The results suggest that water from Goreangab and Swakoppoort dams may have the potential to modulate endocrine systems, and shows physiological toxicity.

Keywords: cytokines, cytotoxicity, endocrine disrupting chemicals, ephemeral rivers, inflammatory response, neurotoxicity, steroid hormones, water quality

African Journal of Aquatic Science 2014, 39(2): 189–198